Unusual Irish lake periodically disappears

Loughareema. A sign posted along a roadside in far northeastern Ireland proclaims this lake's existence, but depending on when you visit, it may or may not be there. That's because Loughareema is Ireland's famous 'Vanishing Lake.'

With phenomena like Loughareema, it's really no wonder that Ireland has such a rich mythology attached to it, but there is a very simple scientific reason for why this lake periodically appears and then vanishes. The rock underneath the topsoil of the region is a very porous form of limestone called chalk (indeed, the same chalk we use in the classroom), which water can pass through very easily.

Loughareema forms over top of what is known as a 'chalk plug-hole' — a spiral drain eroded through the layers of topsoil, that allows water to quickly flow into the porous rock below. When peat gets washed into this hole, it plugs it up and any rainfall in the area accumulates on the surface, forming the small lake. When the peat finally clears, the water quickly and completely drains away, leaving only a muddy patch and a small stream behind.